Make it clearer what Notify is for from homepage

Uses some graphic design to communicate what Notify is:

- for sending messages to lots of people
- messages can be personalised

app/templates/components/phone.html

@@ -0,0 +1,16 @@
+{% macro phone(recipient, message) %}
+  <div class="phone">
+    <div class="phone-speaker"></div>
+    <div class="phone-screen">
+      <h2 class="phone-recipient">
+        <span class="visually-hidden">
+          Example text message
+        </span>
+        To: {{recipient}}
+      </h2>
+      <div class="phone-sms">
+        {{ message }}
+      </div>
+    </div>
+  </div>
+{% endmacro %}